Back hoe type shovels are widely used in earth moving owing to their ability to dig swiftly and efficiently. They are particularly useful in soils, or other materials, that can be readily penetrated by the teeth of the shovel or bucket.
Efficiency is seriously impaired, however, where large rocks, roots, crustaceous layers of earth, asphalt, concrete, ice or other obstacles are encountered.
The market place as well as the patent literature are not lacking in specimens of ripper attachments for back hoe buckets designed to overcome the problems presented by crustaceous surfaces and such other impediments as are frequently encountered in the earth moving field.
U.S. Pat. No. 3,596,996 to Carter, for example, discloses a ripper attachment for a back hoe. It should be noted, however, that the lifting and fracturing effort exerted by the attachment in the Carter patent is limited by the force available at the bucket. That is to say, the vertical ripping effort of the attachment is restricted as a result of the bucket's being located at the end of the dipper which, in turn, is pivoted on the end of the boom. The resultant long moment arm can lift the bucket and the attachment with a considerable amount of force but where large tree roots or very heavy rocks are encountered, the geometry of the elongated moment arm, when taken in conjunction with the available counterbalancing weight of the carrying vehicle, necessarily imposes an upper limit which sometimes falls short of the lifting effort required to do the job.
In summary, there is considerable room for improvement.